Why the contact angle is not applied on this wall?

Hossein1 · January 18, 2017, 23:47

I've created a VOF model for impact of a moving particle onto a water droplet (Vp=7 m/s and Vd=0.7 m/s). The particle is hydrophobic and I'm using wall adhesion model and defined a contact angle of 118 deg for the particle as a wall. However, as you can see in the attached picture, this hydrophobic contact angle does not apply on water-solid interface (its behavior is like a hydrophilic surface).
I've already tried this with a stationary particle and it worked very well (liquid film behavior is normal). I'm not sure if its something related to the dynamic mesh (moving particle) or not.

Any thoughts about the reason is appreciated.

LuckyTran · January 19, 2017, 19:45

What you are specifying in those boxes is the surface tension and contact angle of the water|air interface (near the wall). Hence you did not directly specify any hydrophobic/hydrophillic properties for the wall|water or wall|air.

Is the blue water and red air? Then it would make sense. Remember the 118 is with respect to the fluid in the 1st column.

Hossein1 · January 19, 2017, 20:15

As you can see in the picture, the contact angle box appears in the boundary conditions window (i.e 'wall' in this case, which is actually my particle). Therefore, the value that we enter here is in fact the angle between air-water interface and the wall which is the same as our desired contact angle.
I already got good results in another case (see here), but I don't know why the contact angle doesn't work in this case.
Red is water and blue is air phase.

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January 19, 2017, 19:45		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,762 Rep Power: 66	What you are specifying in those boxes is the surface tension and contact angle of the water\|air interface (near the wall). Hence you did not directly specify any hydrophobic/hydrophillic properties for the wall\|water or wall\|air. Is the blue water and red air? Then it would make sense. Remember the 118 is with respect to the fluid in the 1st column.

January 19, 2017, 20:15		#3
Hossein1 Member Join Date: Jun 2015 Posts: 46 Rep Power: 11	As you can see in the picture, the contact angle box appears in the boundary conditions window (i.e 'wall' in this case, which is actually my particle). Therefore, the value that we enter here is in fact the angle between air-water interface and the wall which is the same as our desired contact angle. I already got good results in another case (see here), but I don't know why the contact angle doesn't work in this case. Red is water and blue is air phase.